The discovery of the particle now identified as the Higgs boson by the ATLAS and CMS experiments [1]}, [2]}, [3]} at the CERN LHC [4]} has opened a new era in the history of particle physics. So far, precise measurements of the Higgs boson spin, parity, width, and couplings in production and decay have been consistent with the expectations for the standard model (SM) Higgs boson [5]}, [6]}, [7]}, [8]}. However, the possibility of exotic Higgs boson decays to new lighter bosons is not excluded, and is proposed in various theories beyond the SM (BSM) [9]}. The LHC combination of the SM Higgs boson measurements at 7 and 8allows Higgs boson decays to BSM states with a rate of up to \(34\%\)  [7]} at 95% confidence level (CL). The LHC data at 13have been used to place an upper limit of about 40% for the Higgs boson branching fraction (\(\mathcal {B}\) ) to BSM particles at 95% CL  [11]}.
